Automatic devices for identifying individuals by means of the iris of the eye comprise one or two cameras for capturing images of the individual's irises. The cameras used present limited depth and width of field which makes it necessary for the individual to be accurately positioned relative to the cameras in order to have images that provide sufficient quality to enable irises to be recognized and the individual to be identified.
Proposals have thus been made to associate the identification apparatus with a device for positioning the user of the identification apparatus.
A positioning device is known that detects the position of the user and sends visual signals to the user enabling the user to correct position if it is not appropriate. Nevertheless, those signals can be wrongly interpreted, making it impossible to achieve correct positioning without the intervention of an operator.
There thus exist positioning devices of the above type associated with a voice synthesis system for giving the user verbal instructions on repositioning. That method nevertheless requires prior knowledge of the language(s) spoken by users and it is difficult to implement in noisy environments. In addition, generating and uttering voice messages is relatively time consuming, and that is incompatible with a maximum duration for identification of the order of 3 minutes that is presently required when the number of people to be identified is large.
To solve those drawbacks, proposals have been made to use a mirror on which there are reference marks for positioning the eyes of the user, a user being correctly positioned when the eyes of the user's reflection on the mirror are superposed on the positioning reference marks. Correcting positioning is then very intuitive. Nevertheless, the reflection of the user and the positioning reference marks do not then lie in the same optical plane. Unfortunately, there exist people who have a preferred eye for positioning in three dimensions. When aligning themselves on the reference marks, such people tend unconsciously to use only that one eye known as the dominant eye. This leads to a parallax error that leads to wrong positioning. In addition, the existence of two optical planes runs the risk of leading to problems of accommodation for a user who cannot see both the reference marks and the user's own reflection in focus simultaneously. These problems of accommodation can be detrimental to positioning.